System and method for reshaping an eye feature

ABSTRACT

A system for applying therapy to an eye includes an applicator having a conducting element configured to direct energy from an energy source to an application end of the conducting element, where the application end has an eye contact portion. A positioning system receives the applicator and positions the eye contact portion in stable engagement with the surface of an eye. In some embodiments, the conducting element is disposed within a housing for the applicator and an adjustment system is employed to move the conducting element relative to the housing. The adjustment system enables controlled movement of the conducting element and the eye contact portion against the corneal surface. In particular embodiments, sufficient contact between the applicator and the cornea is determined by causing applanation of the cornea. In other embodiments, a physical measurement device, such as a strain gauge, is employed to determine when sufficient contact has been established.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains generally to the field of keratoplasty and, moreparticularly, to a system and method for accurately and consistentlyapplying a thermokeratoplasty applicator to the cornea.

2. Description of Related Art

A variety of eye disorders, such as myopia, keratoconus, and hyperopia,involve abnormal shaping of the cornea. Keratoplasty reshapes the corneato correct such disorders. For example, with myopia, the shape of thecornea causes the refractive power of an eye to be too great and imagesto be focused in front of the retina. Flattening aspects of the cornea'sshape through keratoplasty decreases the refractive power of an eye withmyopia and causes the image to be properly focused at the retina.

Invasive surgical procedures, such as laser-assisted in-situkeratonomileusis (LASIK), may be employed to reshape the cornea.However, such surgical procedures typically require a healing periodafter surgery. Furthermore, such surgical procedures may involvecomplications, such as dry eye syndrome caused by the severing ofcorneal nerves.

Thermokeratoplasty, on the other hand, is a noninvasive procedure thatmay be used to correct the vision of persons who have disordersassociated with abnormal shaping of the cornea, such as myopia,keratoconus, and hyperopia. Thermokeratoplasty, for example, may beperformed by applying electrical energy in the microwave or radiofrequency (RF) band. In particular, microwave thermokeratoplasty mayemploy a near field microwave applicator to apply energy to the corneaand raise the corneal temperature. At about 60° C., the collagen fibersin the cornea shrink. The onset of shrinkage is rapid, and stressesresulting from this shrinkage reshape the corneal surface. Thus,application of energy in circular, ring-shaped patterns around the pupilgenerates heat that may cause aspects of the cornea to flatten andimprove vision in the eye. Although thermokeratoplasty has beenidentified as a technique for eye therapy, there is a need for apractical system that enables more accurate and precise application ofthermokeratoplasty in a clinical setting.

SUMMARY OF THE INVENTION

In general, the pattern of energy applied to an eye feature duringthermokeratoplasty depends on the position of the energy applicatorrelative to the eye feature, such as a cornea. Thus, to provide reliableapplication of energy to the eye feature, embodiments according toaspects of the present invention position the applicator in uniform andconstant contact with the eye feature while the applicator provides eyetherapy. In this way, the relationship between the applicator and theeye feature is more definite and the resulting delivery of energy ismore predictable and accurate. The positioning of the applicatorprovides better electrical and thermal contact. Advantageously, theseembodiments also provide a system and method for accurately reproducingsufficient contact between the applicator and the eye feature.

For example, an embodiment provides a system for applying therapy to aneye including an applicator having a conducting element configured todirect energy from an energy source to an application end of theconducting element, where the application end has an eye contactportion. The energy source in this embodiment may be an electricalenergy source, and the conducting element may include an outer electrodeand an inner electrode separated by a gap, where the two electricalconductors define the application end with the eye contact portion. Apositioning system is configured to receive the applicator and positionthe eye contact portion in stable engagement with the surface of an eyeduring the application of energy to a targeted feature of the eye, suchas the cornea.

In some embodiments, the conducting element is disposed within a housingfor the applicator, and an adjustment system is employed to move theconducting element relative to the housing. With the positioning systembeing attached to the eye surface and the applicator housing being fixedrelative to the positioning system, the adjustment system enablescontrolled movement of the conducting element and the eye contactportion against the eye surface to cause sufficient contact with thetargeted eye feature. The adjustment system, for example, may be anelectromechanical system.

In particular embodiments, sufficient contact between the applicator andthe cornea is determined by causing an observable amount of flattening,or applanation, of the cornea. The applanation provides a constant anduniform pressure against the corneal surface. In other embodiments, aphysical measurement device, such as a strain gauge, may be employed todetermine when sufficient contact has been established. With suchapproaches, embodiments can consistently reproduce a specified amount ofcontact.

While some embodiments may move the applicator into contact against thecornea, further embodiments may employ a controlled vacuum source, forexample, to draw or suction the cornea into sufficient contact againstthe applicator.

These and other aspects of the present invention will become moreapparent from the following detailed description of the preferredembodiments of the present invention when viewed in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of an embodiment employing apositioning system that receives and moves an electrical energyconducting element into engagement with the cornea according to aspectsof the present invention.

FIG. 2 illustrates another cross-sectional view of the embodiment ofFIG. 1.

FIG. 3A illustrates an image of a cornea after energy has been applied.

FIG. 3B illustrates another image of the cornea of FIG. 3A.

FIG. 3C illustrates an image of the cornea of FIG. 3A.

FIG. 3D illustrates another image of the cornea of FIG. 3A.

FIG. 4 illustrates an example of a coupling system for adjustablycoupling an energy conducting element to an applicator housing accordingto aspects of the present embodiment.

FIG. 5 illustrates an automated adjustment system for adjustablycoupling an energy conducting element to an applicator housing accordingto aspects of the present embodiment.

FIG. 6 illustrates a cross-sectional view of an embodiment that employsan electromechanical element to position an energy conducting elementaccording to aspects of the present invention.

FIG. 7 illustrates a cross-sectional view of another embodiment thatemploys an electromechanical element to position an energy conductingelement according to aspects of the present invention.

FIG. 8 illustrates a cross-sectional view of an embodiment that employsyet another electromechanical element to position an energy conductingelement according to aspects of the present invention.

FIG. 9 illustrates a cross-sectional view of an embodiment that drawsthe cornea into contact with the energy conducting element according toaspects of the present invention.

FIG. 10 illustrates a cross-sectional view of an embodiment employing apositioning system that receives and moves an optical energy conductingelement into engagement with the cornea according to aspects of thepresent invention.

DETAILED DESCRIPTION

Referring to the cross-sectional view of FIG. 1, a system for applyingenergy to a cornea 2 of an eye 1 to achieve corrective reshaping of thecornea is illustrated. In particular, FIG. 1 shows an applicator 100that includes a housing 110 and an energy conducting element 111, whichextend from a proximal end 100A to a distal end 100B. The energyconducting element 111 is positioned within a passageway 110A whichextends longitudinally through the housing 110. Any number of bearings110B, or similar guiding structures, may be employed to keep the energyconducting element 111 substantially centered within the passageway110A. An electrical energy source 120 is operably connected to theenergy conducting element 111 at the distal end 100B, for example, viaconventional conducting cables. The electrical energy source 120 mayinclude a microwave oscillator for generating microwave energy. Forexample, the oscillator may operate at a microwave frequency range of500 MHz to 3000 MHz, and more specifically at a frequency of around 915MHz which provides safe use of the energy conducting element 111.Although embodiments described herein may employ microwave frequencies,it is contemplated that any frequency, e.g., including microwave,radio-frequency (RF), etc., may be employed. For example, embodimentsmay employ radiation having, but not limited to, a frequency between 10MHz and 300 GHz.

Operation of the energy source 120 causes energy to be conducted throughthe energy conducting element 111 to the distal end 100B. As such, theapplicator 100 may be employed to apply energy to the cornea 2 of theeye 1 which is positioned at the distal end 100B. As shown further inFIG. 1, the distal end 100B is positioned over the cornea 2 by apositioning system 200. In general, the positioning system 200 providessupport for the applicator 100 so that the energy conducting element 111can be operated to deliver energy to targeted areas of the cornea 2. Thepositioning system 200 includes an attachment element 210 which receivesthe applicator housing 110. Meanwhile, the attachment element 210 can befixed to a portion of the eye surface 1A, such as the area surroundingthe portion of the cornea 2 being treated. The attachment element 210situates the applicator 100 in a stable position for delivering energyto the cornea 2.

As shown in FIG. 1, the attachment element 210 of the positioning system200 may have a substantially annular structure defining a centralpassageway 211 through which the applicator housing 110 can be receivedand the cornea 2 can be accessed. In some embodiments, for example, anouter diameter of the annular structure may range from approximately 18mm to 23 mm while an inner diameter may range from approximately 11 mmto 15 mm to accommodate aspects of the eye 1 and the cornea 2. Theattachment element 210 may be attached to portions of the eye surface 1Aby creating a vacuum connection with the eye surface 1A. As such, theattachment element 210 of FIG. 1 acts as a vacuum ring that includes aninterior channel 212 which is operably connected to a vacuum source 140via connection port 217. The attachment element 210 also includes aplurality of openings 216 which open the interior channel 212 to the eyesurface 1A. The attachment element 210 may be formed from abiocompatible material such as a titanium alloy or the like. FIG. 2illustrates a cross-sectional view of the attachment element 210,including the central passageway 211, the interior channel 212, theplurality of openings 216, and the connection port 217. FIG. 2 alsoshows the housing 110 being received within the central passageway 211.

When the openings 216 are positioned in contact with the eye surface 1Aand the vacuum source 140 is activated to create a near vacuum or lowpressure within the interior channel 212, the openings 216 operate tosuction the attachment element 210 and the eye surface 1A together. Topromote sufficient suction between the eye surface 1A and the attachmentelement 210, the bottom surface 213 of the attachment element 210 may becontoured to fit the shape of the eye more closely. In one example, thevacuum source 140 may be a syringe, but the vacuum source 140 may be anymanual or automated system that creates the appropriate amount ofsuction between the attachment element 210 and the eye surface 1A.Although the attachment element 210 can be stably attached to the eyesurface 1A, the attachment element 210 can be detached by removing thevacuum source 140 and equalizing the pressure in the interior channel212 with the exterior environment.

When applying energy to the cornea 2, the applicator 100 may becentered, for example, over the pupil 3, which is generally coincidentwith a center portion 2C of the cornea 2. In some embodiments, thepositioning system 200 may provide an additional receiving element thatis coupled to the attachment element 210 and movable relative to theattachment element 210. The receiving element receives the energyconducting element 111 and can be moved to adjust the position of theenergy conducting element 111 with respect to the attachment element 210and the cornea 2. As such, the energy conducting element 111 can beaccurately positioned over the cornea 2 via the position system. Ingeneral, the positioning system 200 enables the energy conductingelement 111 to apply energy to desired areas of the cornea 2, forexample centered about the pupil 3, to achieve the desired reshaping ofthe cornea 2.

Once the applicator 100 is positioned by the positioning system 200, theenergy conducting element 111 can deliver energy to targeted areas ofcollagen fibers in a mid-depth region 2B of the cornea 2 to shrink thecollagen fibers according to a predetermined pattern and reshape thecornea 2 in a desired manner, thereby improving vision through the eye1. For example, a contribution to the corneal reshaping comes from thecontraction of the collagen fibrils found in the upper third of thecorneal stroma, lying approximately 75-150 microns below the corneal,i.e., epithelial, surface 2A.

As further illustrated in FIG. 1, the electrical energy conductingelement 111 includes two microwave conductors 111A and 111B, whichextend from the proximal end 100A to the distal end 100B of theapplicator 100. For example, as also illustrated in FIG. 2, theconductor 111A may be a substantially cylindrical outer conductor, whilethe conductor 111B may be a substantially cylindrical inner conductorthat extends through an inner passage extending through the outerconductor 111A. With the inner passage, the outer conductor 111A has asubstantially tubular shape. The inner and the outer conductors 111A and111B may be formed, for example, of aluminum, stainless steel, brass,copper, other metals, metal-coated plastic, or any other suitableconductive material. At the distal end 100B of the applicator 100, theouter conductor 111A has a distal surface 111E and the inner conductor111B has a distal surface 111F. As described in further detail below,the distal surfaces 111E and 111F, or portions thereof, provide an eyecontact portion that can be applied against the cornea 2, as shown inFIG. 1. Although the distal surfaces 111E and 111B in FIG. 1 appear tobe located at substantially the same position along the Z-axis, it iscontemplated that the distal surface 111E of the outer electrode 111Amay extend past the distal surface 111F of the inner electrode 111B, oralternatively, the position of the distal surface 111F may be in arecessed position with respect to the distal surface 111E.

With the concentric arrangement of conductors 111A and 111B shown inFIG. 2, a substantially annular gap 111C of a selected distance isdefined between the conductors 111A and 111B. The annular gap 111Cextends from the proximal end 100A to the distal end 100B. A dielectricmaterial 111D may be used in portions of the annular gap 111C toseparate the conductors 111A and 111B. The distance of the annular gap111C between conductors 111A and 111B determines the penetration depthof microwave energy into the cornea 2 according to established microwavefield theory. Thus, the microwave conducting element 111 receives, atthe proximal end 100A, the electrical energy generated by the electricalenergy source 120, and directs microwave energy to the distal end 111B,where the cornea 2 is positioned in accordance with the positioningsystem 200.

The outer diameter of the inner conductor 111B is preferably larger thanthe pupil 3, over which the applicator 100 is centered. In general, theouter diameter of the inner conductor 111B may be selected to achieve anappropriate change in corneal shape, i.e. keratometry, induced by theexposure to microwave energy. The outer diameter of the inner electrode111B determines the diameter across which the refractive change to thecornea 2 is made. When the energy conducting element is applied to thecorneal surface 2A, the area of the cornea 2 at the periphery of theinner electrode 111B is subject to an energy pattern with substantiallythe same shape and dimension as the gap 111C between the two microwaveconductors 111A and 111B.

Meanwhile, the inner diameter of the outer conductor 111A may beselected to achieve a desired gap between the conductors 111A and 111B.For example, the outer diameter of the inner conductor 111B ranges fromabout 4 mm to about 10 mm while the inner diameter of the outerconductor 111A ranges from about 4.1 mm to about 12 mm. In some systems,the annular gap 111C may be sufficiently small, e.g., in a range ofabout 0.1 mm to about 2.0 mm, to minimize exposure of the endotheliallayer of the cornea (posterior surface) to elevated temperatures duringthe application of energy by the applicator 100.

A controller 130 may be employed to selectively apply the energy anynumber of times according to any predetermined or calculated sequence.In addition, the energy may be applied for any length of time.Furthermore, the magnitude of energy being applied may also be varied.Adjusting such parameters for the application of energy determines theextent of changes that are brought about within the cornea 2. Of course,the system attempts to limit the changes in the cornea 2 to anappropriate amount of shrinkage of collagen fibrils in a selectedregion. When applying microwave energy to the cornea 2 with theapplicator 100, the microwave energy may be applied with low power (ofthe order of 40 W) and in long pulse lengths (of the order of onesecond). However, other systems may apply the microwave energy in shortpulses. In particular, it may be advantageous to apply the microwaveenergy with durations that are shorter than the thermal diffusion timein the cornea. For example, the microwave energy may be applied inpulses having a higher power in the range of 500 W to 3 KW and a pulseduration in the range of about 10 milliseconds to about one second.

Referring again to FIG. 1, at least a portion of each of the conductors111A and 111B may be covered with an electrical insulator to minimizethe concentration of electrical current in the area of contact betweenthe corneal surface (epithelium) 2A and the conductors 111A and 111B. Insome systems, the conductors 111A and 111B, or at least a portionthereof, may be coated with a material that can function both as anelectrical insulator as well as a thermal conductor. A dielectricmaterial 111D may be employed along the distal end 100B of theapplicator 100 to protect the cornea 2 from electrical conductioncurrent that would otherwise flow into the cornea 2 via conductors 111Aand 111B. Such current flow may cause unwanted temperature effects inthe cornea 2 and interfere with achieving a maximum temperature withinthe collagen fibrils in a mid-depth region 2B of the cornea 2.Accordingly, the dielectric material 111D is positioned between theconductors 111A and 111B and the cornea 2. In particular, as shown inFIG. 1, the distal surfaces 111E and 111F of the conductors 111A and111B include a dielectric material 111D. The dielectric material 111Dmay be sufficiently thin to minimize interference with microwaveemissions and thick enough to prevent superficial deposition ofelectrical energy by flow of conduction current. For example, thedielectric material 111D may be a biocompatible material, such asTeflon®, deposited to a thickness of about 0.002 inches. In general, aninterposing layer, such as the dielectric material 111D, may be employedbetween the conductors 111A and 111B and the cornea 2 as long as theinterposing layer does not substantially interfere with the strength andpenetration of the microwave radiation field in the cornea 2 and doesnot prevent sufficient penetration of the microwave field and generationof a desired energy pattern in the cornea 2. Of course, the dielectricmaterial 111D may be omitted and electrical energy in the microwave orradio frequency (RF) band may be applied directly. A similarelectrically insulating material 111H may also be employed on the outersurface of the outer electrode 111A.

During operation, the distal end 100B of the applicator 100 as shown inFIG. 1 is positioned by the positioning system 200 at the cornealsurface 2A. The applicator 100 positions the energy conducting element111 to make direct contact with the corneal surface 2A. As such, thedistal surfaces 111E and 111F of the conductors 111A and 111B,respectively, are positioned against the corneal surface 2A. Thepositioning of the conductors 111A and 111B helps ensure that thepattern of microwave energy in the corneal tissue has substantially thesame shape and dimension as the gap 111C between the two microwaveconductors 111A and 111B.

As shown in FIG. 1, the applicator 100 may also employ a coolant system112 that selectively applies coolant to the corneal surface 2A tominimize heat-related damage to the corneal surface 2A duringthermokeratoplasty and to determine the depth of energy delivered belowthe corneal surface 2A to the mid-depth region 2B. Such a coolant systemenables the energy conducting element 111 to be placed into directcontact with the corneal surface 2A without causing heat-related damage.In some embodiments, the coolant may also be applied after theapplication of energy to preserve, or “set,” the desired shape changesby eliminating further presence of energy and preventing further changesto the new corneal shape. Examples of such a coolant system aredescribed in U.S. application Ser. No. 11/898,189, filed Sep. 10, 2007,the contents of which are entirely incorporated herein by reference. Forexample, the coolant delivery system 112 as well as a coolant supply 113may be positioned within the annular gap 111C. Although FIG. 1 mayillustrate one coolant delivery system 112, the applicator 100 mayinclude a plurality of coolant delivery systems 112 arrangedcircumferentially within the annular gap 111C. The coolant supply 113may be an annular container that fits within the annular gap 111C, withthe coolant delivery element 112 having a nozzle structure 112Aextending downwardly from the coolant supply 113 and an opening 112Bdirected toward the distal end 100B. The coolant may be a liquidcryogen, such as tetrafluorothane. Alternatively, the coolant may be acool gas, such as nitrogen gas, e.g., blowoff from a liquid nitrogensource.

In some embodiments, the coolant system 112 is operated, for example,with the controller 130 to deliver pulses of coolant in combination withthe delivery of energy to the cornea 2. Advantageously, applying thecoolant in the form of pulses can help prevent the creation of a fluidlayer between the conductors 111A and 111B and the corneal surface 2Athat interferes with the delivery of energy from the energy conductingelectrode 111. In particular, the short pulses of coolant may evaporatefrom the corneal surface 2A or may be removed, for example, by a vacuum(not shown) before the application of the microwave energy. Rather thancreating an annular energy pattern according to the dimensions of theconductors 111A and 111B, the presence of a fluid layer maydisadvantageously cause a less desirable circle-shaped microwave energypattern in the cornea 2 with a diameter less than that of the innerconductor 111B. Therefore, to achieve a desired microwave pattern insome embodiments, a substantial flow of coolant or a cooling layer doesnot exist over the corneal surface 2A during the application of energyto the cornea 2. To further minimize the presence of a fluid layer, asdescribed previously, the coolant may actually be a cool gas, ratherthan a liquid coolant.

Additionally or alternatively, heat sinks may also be employed to directheat away from the corneal surface 2A and reduce the temperature at thesurface 2A.

FIGS. 3A-D illustrate an example of the effect of applying energy tocorneal tissue with a system for applying energy, such as the systemillustrated in FIG. 1. In particular, FIGS. 3A and 3B illustrate highresolution images of the cornea 2 after energy has been applied. AsFIGS. 3A and 3B show, a lesion 4 extends from the corneal surface 3A toa mid-depth region 3B in the corneal stroma 2D. The lesion 4 is theresult of changes in corneal structure induced by the application ofenergy as described above. These changes in structure result in anoverall reshaping of the cornea 2. It is noted that the application ofenergy, however, has not resulted in any heat-related damage to thecorneal tissue.

As further illustrated in FIGS. 3A and 3B, the changes in cornealstructure are localized and limited to an area and a depth specificallydetermined by an applicator as described above. FIGS. 3C and 3Dillustrate histology images in which the tissue shown in FIGS. 3A and 3Bhas been stained to highlight the structural changes induced by theenergy. In particular, the difference between the structure of collagenfibrils in the mid-depth region 2B where energy has penetrated and thestructure of collagen fibrils outside the region 2B is clearly visible.Thus, the collagen fibrils outside the region 2B remain generallyunaffected by the application of energy, while the collagen fibrilsinside the region 2B have been rearranged and form new bonds to createcompletely different structures. In sum, the corneal areas experience athermal transition to achieve a new state.

The embodiments described herein provide a system and method by whichthe application of energy can accurately and precisely provide thechanges in corneal shape that provide the desired improvements in theeye. Unlike other approaches, the embodiments provide consistent andreproducible results, especially to enable the eye therapy to be used ina clinical setting. As described previously, the energy pattern appliedby the energy conducting element 111 may be affected by an intermediatefluid layer that interferes with the contact between the energyconducting element 111 and the corneal surface 2A. In general, theapplication of energy to the cornea 2 depends in part on the position ofthe distal surfaces 111E and 111F relative to the corneal surface 2A. Asa result, to provide reliable application of energy to the cornea 2,embodiments ensure that the distal surfaces 111E and 111F are positionedto make contact with the corneal surface 2A. In this way, therelationship between the energy conducting element 411 and the cornea 2is more definite and the resulting delivery of energy is morepredictable and accurate.

In some embodiments, sufficient contact is determined by causing anobservable amount of flattening, or applanation, of the cornea. Theapplanation provides a constant and uniform pressure against the cornealsurface 2A. For example, as illustrated in FIG. 1, the applicator 100can position the energy conducting element 111 against the cornealsurface 2A so that the distal surface 111E of the outer electrode 111Aand the distal surface 111F of the inner electrode 111B flattens thecornea 2. Although the distal surfaces 111E and 111F, or portionsthereof, in contact with the corneal surface 2A are substantially flat,it is understood that the surfaces 111E and 111F may be shaped, e.g.contoured, in other ways to cause the desired contact. As shown in FIG.1, the inner edge of the distal surface 111E of the outer electrode 111Amay be beveled, or otherwise shaped, to minimize any pinching of thecornea 2 that may occur between the outer electrode 111A and the innerelectrode 111B when the distal surfaces 111E and 111F are appliedagainst the cornea 2. The applanation described herein adds precisionand accuracy to the eye therapy procedure, particularly by improvingelectrical and thermal contact between the distal surfaces 111E and 111Fand the corneal surface 2A.

The housing 110 and the positioning system 200 combine to keep thedistal surfaces 111E and 111F in contact with the corneal surface 2A andmaintain the applanation of the cornea 2 as energy is delivered via theenergy conducting element 111. In addition, the housing 110 and thepositioning system 200 combine to enable reproducible and predictablecontact between the distal surfaces 111E and 111F and the cornealsurface 2A. For example, as shown in FIG. 1, a first coupling system 114may be employed to couple the housing 110 to the attachment element 210of the positioning system 200. Once the housing 110 is guided fully intothe attachment 210, the first coupling system 114 prevents the housing110 from moving relative to the attachment element 210 along the Z-axisshown in FIG. 1.

As shown further in FIG. 1, the first coupling system 114 may includeconnecting elements 114A, which extend transversely from the attachmentelement 210 into cavities 114B in the applicator housing 110. As such,the applicator 110 is guided into the passageway 211 until the cavities114B reach and engage the connecting elements 114A. In this way, theapplicator 100 homes to a position determined by the connecting elements114A, which act as stops. As such, the applicator 110 can be receivedinto the same position relative to the attachment element 210 each time.The connecting elements 114A may be retractable to facilitate removal ofthe housing 110 from the attachment element 210. For instance, theconnecting elements 114A may be rounded structures that extend from thehousing 110 on springs (not shown).

It is understood, however, that the first coupling system 114 may employother techniques, e.g. mechanically interlocking or engaging structures,for coupling the housing 110 to the attachment element 210. For example,the central passageway 211 of the attachment element 210 may have athreaded wall which receives the housing 110 in threaded engagement. Insuch an embodiment, the housing 110 may be screwed into the attachmentelement 210. The applicator can then be rotated about the Z-axis andmoved laterally along the Z-axis to a desired position relative to thecornea 2. Stops may be included on the attachment element 210 todetermine the target position of the applicator 100 in the passageway211.

While the attachment element 210 keeps the applicator housing 110 instable position relative to the cornea 2, the housing 110 in turnensures that the distal surfaces 111E and 111F of the energy conductingelement 111 maintain the desired amount of pressure against the cornea2. For example, as shown in FIG. 1, a second adjustable coupling system115 may be employed to couple the energy conducting element 110 to thehousing 110. With the energy conducting element 111 positioned in thepassageway 110A, the second coupling system 115 prevents the energyconducting element 111 from moving relative to the housing 110 along theZ-axis. For example, as illustrated in FIG. 1, the second couplingsystem 115 may include a connecting element 115A, such as a pin-likestructure, which is positioned along the housing 110 and extendsinwardly from the housing 110 into a cavity of a receiving structure115B on the energy conducting element 111. Like the first couplingsystem 114, the second coupling system 115, of course, may employ othertechniques for coupling the energy conducting element 111 to the housing110. For example, in other embodiments, the energy conducting element111 may be simply fastened or bonded to the inner walls of the housing110 according to conventional methods. In general, the electricalconducting element 111, the housing 110, and the attachment element 210are all fixed relative to each other while the attachment element 210 isattached to the corneal surface 2A. Accordingly, the energy conductingelement 111 is able to apply constant pressure against the cornealsurface 2A and flatten the cornea 2. The coupling systems 114 and 115reproducibly determines the position of the energy conducting element111 with respect to the cornea 2.

The positions of the connecting element 115A and/or the receivingstructure 115B may be adjustable to enable the energy conducting element111 to occupy a selected position within the housing 110 and provide adesired amount of applanation. For example, as shown in FIG. 4, theconnecting element 115A may be a threaded pin that is screwed into acorresponding threaded cavity 115C in the receiving structure 115B. Oncethe connecting element 115A is fully screwed into the cavity 115C, ahead 115E of the connecting element 115A and the receiving structure115B are held against the housing 110 by sufficient contact and frictionto prevent movement of the connecting element 111A and the energyconducting element 111 along the Z-axis. The connecting element 115A canbe positioned at various points in a slot, or opening, 115D that extendsalong the Z-axis in the housing 110. Therefore, the energy conductingelement 111 can be moved to different positions along the Z-axisrelative to the housing 110, and the connecting element 115A can becorrespondingly moved in the slot 115 to be screwed into the receivingelement 115B and couple the energy conducting element 111 to the housing110. With the housing 110 fixed to the attachment element 210 on thecorneal surface 2A, the ability to change the position of the energyconducting element 111 relative to the housing 110 means that theposition of the distal ends 111E and 111F of the energy conductingelement 111 relative to the corneal surface 2A can be changed. As aresult, the amount of pressure on the cornea 2 can be adjusted toprovide a particular amount of applanation. As long as the connectingelement 115A remains in the same position relative to the housing 110,the particular amount of applanation is reproducible.

FIG. 5 illustrates the movement of the energy conducting element 111toward the cornea 2 within the housing 110 which is fixed relative tothe cornea 2 with the attachment element 210. Although adjusting theposition of the energy conducting element 111 relative to the housing110 may be achieved manually, a more automated adjustment system 300, asshown in FIG. 5, can be employed to adjustably couple the energyconducting element 111 to the housing 110. Advantageously, theadjustment system 300 facilitates the accurate positioning of the energyconducting element 300 against the corneal surface 2A. After theattachment element 210 is fixed to the eye surface 1A, the applicator100 is guided into position within the passageway 211 of the attachmentelement 210, and the adjustment system 300 can be easily operated tomove the distal surfaces 111E and 111F of the energy conducting element111 against the corneal surface 2A.

The adjustment system 300 may be further connected to a user interfacesystem 305 that accepts input from a user and correspondingly operatesthe adjustment system 300. The user interface system 305, for example,may be a device with a keypad to receive input from a user. The keypadmay be part of a processing system, such as a conventional personalcomputer, with software to control the adjustment system 300.Alternatively, the user interface system 305 may be a device, such as ajoystick, that receives instructions from the user through moremechanically oriented input.

FIG. 5 illustrates the downward movement of the energy conducting device111 relative to the housing 110 and the positioning system 200 and intocontact with the corneal surface 2A. One or more stops may be employedto determine the extent of the downward movement of the energyconducting element 111 against the cornea 2. As described previously,the energy conducting device 111 may applied to cause applanation of thecornea 2, similar to the applanation shown in FIG. 1. The applanationindicates that sufficient contact has been established between theenergy conducting device 111, i.e., the distal contact surfaces 111E and111F, and the corneal surface 2A.

On the other hand, as shown further in FIG. 5, a physical measurementdevice 340 may be employed with the adjustment system 300 to measure theamount of pressure being applied by the distal surfaces 111E and 111Fagainst the cornea 2. For example, the physical measurement device 340may be a strain gauge that is able to detect the deformation in theenergy conducting element 111 caused by contact with the corneal surface2A. Therefore, the physical measurement device 340 indicates when theenergy conducting element 111 has made sufficient contact with thecorneal surface 2A and is applying constant and uniform pressure. As aresult, applanation is not necessary to receive an indication thatsufficient contact has been established with the cornea 2. The physicalmeasurement device 340 also enables the application of a certainpressure to be reliably and accurately reproduced.

As illustrated in FIG. 6, the adjustment system 300 may be anelectromechanical system 310 that includes a motor 311 connected to aconfiguration 312 of one or more gears 313 coupled to the housing 110.The gears 313 in turn engage corresponding teeth 314 that are alignedparallel with the Z-axis and extend outwardly from the energy conductingelement 111. As such, operation of the motor 311, via a user interfacesystem 305, causes rotation of the gears 313 and corresponding movementof the teeth 314 and thus the energy conducting element 111 along theZ-axis.

To prevent the energy conducting element 111 from moving too far againstthe corneal surface 2A, a safety mechanism 116 may be employed as shownin FIG. 6. In particular, the energy conducting element 111 can movetoward or against the corneal surface 2A until a stop 116B, whichextends outwardly from, and moves with, the energy conducting element111, makes contact with a corresponding stop extending inwardly from thehousing 110. In other words, the stop 116A is positioned to blockfurther movement of the block 116B and the energy conducting element 111past a particular point along the Z-axis. In addition, FIG. 6 shows abearing 110B that extends inwardly from the housing 110 and ispositioned opposite the gear 113 to position the energy conductingelement 111 within the passageway 110A of the housing 110. To ensurethat the teeth 314 extending outwardly from the energy conductingelement 111 properly engage the gear 113, a spring 110G may be employedto bias the energy conducting element 111 toward the gear 113. Asdescribed previously, any number of such bearings, or guiding elements,110B may be employed within the housing 110. As shown in FIG. 6, springs110G may be employed with any of these bearings 110B.

Like other embodiments described herein, the electromechanical system310 may be applied to cause applanation of the cornea 2 to ensuresufficient contact has been established between the energy conductingdevice 111, i.e., the distal contact surfaces 111E and 111F, and thecorneal surface 2A. Alternatively, as shown in FIG. 5, a physicalmeasurement device 340, such as a strain gauge, may be employed with theelectromechanical system 310 to measure the amount of pressure beingapplied by the distal surfaces 111E and 111F against the cornea 2. Whenoperation of the motor 311 drives the gears 313 to cause the energyconducting element 111 to apply a force on the cornea 2, thecorresponding reaction force acting on the energy conducting element 111and the gears 313 acting on the teeth 314 place the energy conductingelectrode in a state of compression. The physical measurement device 340measures the amount of compression and the measurement can be translatedinto the pressure being applied to the cornea 2. A threshold pressuremeasurement corresponding to a desired amount of contact between theenergy conducting electrode 111 and the cornea 2 can be determined. Ingeneral, the threshold value corresponds to the first instance ofconstant and uniform application of pressure on the cornea 2. Therefore,once the measured pressure reaches this threshold value, furtherdownward movement of the energy conducting element 111 against thecorneal surface 2A is not necessary. As such, causing applanation of thecornea 2 is also not necessary. In addition, the physical measurementdevice 340 also enables the application of a certain pressure to bereliably and accurately reproduced.

FIG. 7 illustrates another adjustment system 300 that employs anelectromechanical system 320 including a motor 321 connected to analternative configuration 322 of one or more gears 323 connected to thehousing 110. FIG. 7 demonstrates that a variety of gear configurationsmay be employed according to aspects of the present invention. A gearconfiguration may be selected, for instance, according to the desiredgeometry of the assembled system. In particular, the configuration 322in FIG. 7 includes gears 323A which cause a worm 323B to rotate about anaxis parallel with the Z-axis. The worm 323B which is operably coupledto the housing 110 engages teeth 324 operably coupled to the energyconducting element 111. The teeth 324 are aligned parallel to the Z-axisand the rotation of the worm 323B causes the teeth 324 and the energyconducting element 111 to move along the Z-axis. The embodiment of FIG.7 may employ a safety mechanism 116, as described previously. Inaddition, any number of such bearings, or guiding elements, 110B may beemployed within the housing 110.

It is contemplated that additional intermediate structures may beemployed to couple the energy conducting element 111 to the housing 110.For example, as shown in FIG. 7, rather than attaching the teeth 324directly to an outer surface of the energy conducting element 111, theteeth 324 extend outwardly from an intermediate structure, orcylindrical structure, 117. The energy conducting element 111 isenclosed in a chamber 117A defined by the cylindrical structure 117, sothat movement of the cylindrical structure 117 causes correspondingmovement of the energy conducting element 111. The energy conductingelement 111 may be clipped into, or otherwise coupled or attached to,the cylindrical structure 117. Of course, any connections to the energyconducting element 111, for example, with the electrical energy source(not shown), can be made through the wall(s) of the cylindricalstructure 117. Advantageously, the energy conducting element 111 is notrequired to accommodate specific aspects of the adjustment system 300.In the embodiment of FIG. 7, the energy conducting element 111 does nothave to include the teeth 324, as the teeth 324 are provided with thecylindrical structure 117. Because energy conducting elements 111specially designed for the adjustment system 300 are not required, theapplicator housing 110 is more easily compatible with different energyconducting elements 111. It is therefore contemplated that embodimentsmay include reusable applicator housings with replaceableinterchangeable energy conducting elements 111.

Although the embodiments of FIGS. 6 and 7 employ electromechanicalsystems with gears, it is understood that other types of systems can beused to provide controlled movement of the energy conducting element 111within the housing 110. For example, the electromechanical system 330shown in FIG. 8 employs a piezoelectric system. In particular, apiezoelectric element, or material, 331 couples the energy conductingelement 111 to the housing 110 and is connected to an electrical source332. When the electrical source 332 is operated by the user interfacesystem 305 to apply an electric field to the piezoelectric element 331,the piezoelectric element 331 expands or contracts along the Z-axisdepending on the electric field. Because the energy conducting element111 is coupled to the piezoelectric element 331, as shown in FIG. 8, theenergy conducting element 111 is correspondingly moved in along theZ-axis.

It is also contemplated that the applicator 100 in alternativeembodiments may draw the cornea 2 into desired contact with the energyconducting element 111. As FIG. 9 illustrates, the energy conductingelement 111 may be positioned over the cornea 111. However, rather thanmoving the energy conducting element 111 against the corneal surface 2A,a vacuum source 350 is operated by a controller 130 to create a vacuum,or near vacuum, within the applicator 100 and draw or suction thecorneal surface 2A into contact with the distal surfaces 111E and 111F.A physical measurement device 340 may be employed to indicate to thecontroller 130 that sufficient contact has been established. Forexample, if the physical measurement device 340 is a strain gauge, thestrain gauge measures how much the energy conducting element 111 isbeing compressed as the cornea is drawn against the distal surfaces 111Eand 111F by increasing suction levels from the vacuum source 350. Oncethe physical measurement device 340 signals that a desired thresholdvalue has been achieved, the controller 130 maintains the level ofvacuum to keep the cornea 2 in sufficient contact with the energyconducting electrode 111. It is noted that the controlled vacuum source350 may be used in combination with an adjustment system that canposition the energy conducting electrode 111 over the cornea 2 beforethe vacuum source 350 is operated.

Although the energy conducting element 111 in the previous embodimentsconduct electrical energy to the cornea 2, it is also contemplated thatother systems may be employed to apply energy to cause reshaping of thecornea. As shown in FIG. 10, another embodiment employs an applicator400 that includes a housing 410 and an optical energy conducting element411. The optical energy conducting element 411 passes through apassageway 410A in the housing 410 and is operably connected to anoptical energy source 420, for example, via conventional optical fiber.Any number of bearings, or similar guiding structures, 410B may beemployed to position the optical energy conducting element 411 withinthe housing 410. The optical energy source 420 may include a laser, alight emitting diode, or the like. The optical energy conducting element411 extends to a distal end 400B from a proximal end 400A, where it isoperably connected with the optical source 420. The optical energyconducting element 411 includes an optical fiber 411A. Thus, the opticalfiber 411A receives optical energy from the optical energy source 420 atthe proximal end 400A and directs the optical energy to the distal end400B, where the cornea 2 of an eye 1 is positioned. A controller 430 maybe operably connected to the optical energy source 420 to control thedelivery, e.g. timing, of the optical energy to the optical conductingelement 411. The optical energy conducting element 411 irradiates thecornea 2 with the optical energy and delivers energy for appropriatelyshrinking collagen fibers in the mid-depth region 2B of the cornea 2. Asalso illustrated in FIG. 10, the optical conducting element 411 mayinclude an optical focus element 411B, such as a lens, to focus theoptical energy and to determine the pattern of irradiation for thecornea 2. The distal end 400B of the optical conducting element 411,e.g., the optical focus element 411B, may include an eye contact surface411C that makes constant and uniform contact with the cornea surface 2A.The application of energy to the cornea 2 may depend in part on theposition of the optical conducting element 411 relative to the cornealsurface 2A. As a result, to provide reliable application of energy tothe cornea 2, embodiments ensure that the eye contact surface 411C ispositioned to make contact with the corneal surface 2A. In this way, therelationship between the optical conducting element 411 and the cornea 2is more definite and the resulting delivery of energy is morepredictable. In some embodiments, sufficient contact is determined bycausing an observable amount of flattening, or applanation, of thecornea, as shown in FIG. 10. In other embodiments, a physicalmeasurement device, similar to device 340 above, may be employed tomeasure the amount of pressure being applied against the corneal surface2A, so that applanation is not necessary to ensure that the eye contactsurface 411C is in constant and uniform contact with the corneal surface2A.

As shown in FIG. 10, the applicator 400 may also employ a coolant system412 that selectively applies coolant to the corneal surface 2A. Thecoolant delivery system 412 as well as a coolant supply 413 may bepositioned adjacent to the optical energy conducting element 411. Thecoolant system 412 may be operated, for example, with the controller 430to deliver pulses of coolant in combination with the delivery of energyto the cornea 2. Applying the coolant in the form of pulses can helpminimize the creation of a fluid layer between the optical energyconducting element 411 and the corneal surface 2A providing theadvantages described previously.

As further illustrated in FIG. 10, the applicator 400 and the opticalenergy conducting element 411 are positioned over the cornea 2 by thepositioning system 200 to deliver the optical energy to targeted areasof the cornea 2. The positioning system 200 is employed in the samemanner similar to the previous embodiments. In particular, thepositioning system 200 places the distal end 400B of the applicator 400in a stable position over the cornea 2. For example, as describedpreviously, a first coupling system 414 may be employed to couple thehousing 410 to the attachment element 210 of the positioning system 200.The first coupling system 414 may include connecting elements 414A onthe attachment element 210 that are received into cavities 414B on theapplicator housing 410. Once the housing 410 is fully received into theattachment 210, the first coupling system 414 prevents the housing 410from moving relative to the attachment element 210 along the Z-axis.

In addition, a second coupling system 415 is employed to couple theoptical energy conducting element 410 to the housing 410. With theoptical energy conducting element 411 positioned in the passageway 410A,the second coupling system 415 prevents the energy conducting element411 from moving relative to the housing 410 along the Z-axis. Forexample, as illustrated in FIG. 10, the second coupling system 415 mayinclude a connecting element 415A, such as a pin-like structure, whichextends inwardly from the housing 410 into a cavity of a receivingstructure 415B on the energy conducting element 411. Like the firstcoupling system 414, the second coupling system 415, of course, mayemploy other techniques for coupling the energy conducting element 411to the housing 410. In general, the electrical conducting element 411,the housing 410, and the attachment element 210 are all fixed relativeto each other while the attachment element 210 is attached to thecorneal surface 2A. Accordingly, the optical conducting element 411 isable to apply constant pressure against the corneal surface 2A.

Alternatively, an automated adjustment system, as described previously,may be employed in a system using an optical energy conducting element411. In particular, the automated adjustment system couples the opticalenergy conducting element 411 to the applicator housing 410, but allowselectromechanically controlled movement of the optical energy conductingelement 411 relative to the housing 410 along the Z-axis. With thehousing 410 stably coupled to the attachment element 210 fixed to theeye surface 2A, the optical energy conducting element 411 may be movedinto contact with the corneal surface 2A to provide a flatteningpressure on the cornea.

Accordingly, embodiments according to aspects of the present inventionprovide a system and method for applying a thermokeratoplasty applicatorto the cornea. In particular, embodiments provide a system and methodfor positioning the applicator over the cornea so that the applicatorcan cause the desired amount of flattening of a cornea and improvevision through the cornea. For example, embodiments may provide theapplicator with an eye contact surface that is moved manually,electromechanically, etc. into contact with the corneal surface tophysically flatten the cornea as energy is also delivered to the cornea.Advantageously, embodiments provide an improved system and method thatfacilitates handling and positioning of the applicator to achieve thedesired reshaping of a cornea.

While various embodiments in accordance with the present invention havebeen shown and described, it is understood that the invention is notlimited thereto. The present invention may be changed, modified andfurther applied by those skilled in the art. For example, although theapplicators 200 and 400 in the examples above are separate elementsreceived into the positioning system 200, the applicator 200 or 400 andthe positioning system 200 may be combined to form a more integrateddevice. Thus, embodiments may include an integrated applicator housingand positioning system that receives and positions an energy conductingelement against the cornea. Additionally, although the attachmentelement 210 in the embodiments above may be a vacuum device which isauctioned to the eye surface, it is contemplated that other types ofattachment elements may be employed. For instance, the attachmentelement may be fixed to other portions of the head. Therefore, thisinvention is not limited to the detail shown and described previously,but also includes all such changes and modifications.

It is also understood that the Figures provided in the presentapplication are merely illustrative and serve to provide a clearunderstanding of the concepts described herein. The Figures are not “toscale” and do not limit embodiments to the specific configurations andspatial relationships illustrated therein. In addition, the elementsshown in each Figure may omit some features of the illustratedembodiment for simplicity, but such omissions are not intended to limitthe embodiment.

What is claimed is:
 1. A system for applying therapy to an eye, thesystem comprising: an applicator including a conducting elementconfigured to direct energy from an energy source to an application endof the conducting element, the conducting element including an outerconductor and an inner conductor separated by a gap, the application endhaving an eye contact portion; a positioning system configured toreceive the applicator and position the eye contact portion inengagement against a surface of an eye, the engagement creating acontact pressure between the eye contact portion and a feature of theeye, and the applicator being configured to direct energy to the eyeaccording to the engagement; and a coupling system including: ameasurement device operable to measure the contact pressure between theeye contact portion and the feature of the eye and generate a firstsignal indicative of the measured contact pressure, a controllerconfigured to receive, from the measurement device, the first signalindicative of the measured contact pressure between the eye contactportion, analyze the first signal, and generate a second signal based onthe analysis of the first signal, and an electromechanical adjustmentsystem configured to move, relative to the positioning system, the outerconductor and the inner conductor within the positioning system inresponse to the second signal received from the controller.
 2. Thesystem according to claim 1, wherein the engagement is configured tocause applanation of the feature of the eye.
 3. The system according toclaim 1, wherein the eye contact portion includes a planar surface. 4.The system according to claim 1, wherein the outer conductor and theinner conductor define the application end with the eye contact portion.5. The system according to claim 4, wherein the eye contact portionincludes an edge on the outer electrode that is beveled.
 6. The systemaccording to claim 1, wherein the engagement is configured to cause thesurface of the eye to be drawn into contact with the eye contactportion.
 7. The system according to claim 6, further comprising a vacuumsource configured to draw the surface of the eye into the engagementwith the eye contact portion.
 8. The system according to claim 1,wherein the applicator includes a housing and the conducting element isdisposed within the housing.
 9. The system according to claim 8, whereinthe coupling system is configured to controllably move the conductingelement relative to the housing.
 10. The system according to claim 8,wherein the eye contact portion of the conducting element extends from adistal end of the housing.
 11. The system according to claim 8, furthercomprising a second coupling system for fixedly coupling the housing tothe positioning system.
 12. The system according to claim 1, wherein theelectromechanical device includes a motorized gear configuration. 13.The system according to claim 1, wherein the electromechanical deviceincludes a piezoelectric element.
 14. The system according to claim 1,wherein the positioning system includes an adjustable attachment elementconfigured to be removably attached to the surface of the eye, theattachment element centering the conducting element over the feature ofthe eye.
 15. The system according to claim 14, wherein the attachmentelement includes a vacuum ring configured to create a vacuum connectionwith the surface of the eye.
 16. The system according to claim 14,wherein the positioning system further includes a receiving elementoperably coupled to the attachment element and movable relative to theattachment element, the receiving element being configured to receivethe applicator, and further comprising a movement element controllingthe movement of the receiving element relative to the attachmentelement.
 17. The system according to claim 1, wherein the couplingsystem is configured to transduce rotational movement provided by amotor into linear movement of the conducting element.
 18. The systemaccording to claim 1, wherein the measurement device is a strain gauge.19. A method for applying therapy to an eye, the method comprising:attaching a positioning system to a surface of an eye, the positioningsystem having an aperture providing access to a feature of the eyewithin the aperture; coupling a conducting element to the positioningsystem such that the conducting element is received in the aperture ofthe positioning system and positioned relative to the feature of theeye, the conducting element being operably connected to an energysource, the conducting element having an application end for directingenergy to the eye, the application end having an eye contact portion;with the conducting element coupled to the positioning system, movingthe conducting element in at least a first direction relative to thepositioning system, the first direction being generally perpendicular toan axis of the aperture; measuring, using a measurement device, anamount of contact between the eye contact portion and the feature of theeye; providing a first signal indicative of the measured amount ofcontact to a controller; providing a second signal from the controllerto an adjustment system based on the first signal; moving the eyecontact portion in a second direction relative to the positioningsystem, using the adjustment system controlled by the controller, basedon the second signal, the second direction being generally parallel tothe axis of the aperture; and directing energy from the energy source tothe feature of the eye via the application end.
 20. The method accordingto claim 19, further comprising moving the eye contact portion intoengagement with the feature of the eye.
 21. The method according toclaim 19, further comprising drawing the feature of the eye intoengagement with the eye contact portion.
 22. The method according toclaim 21, wherein the step of drawing the feature of the eye comprisesoperating a vacuum source to suction the feature of the eye intoengagement with the eye contact portion.
 23. The method according toclaim 19, further comprising positioning the conducting element into anapplicator housing having the adjustment system.
 24. The methodaccording to claim 23, wherein the moving the eye contact portionincludes operating an electromechanical device.
 25. The method accordingto claim 19, further comprising determining, using the controller,whether a specified amount of contact between the eye contact portionand the feature of the eye has been established.
 26. The methodaccording to claim 25, wherein the step of determining whether aspecified amount of contact has been established comprises causingapplanation of the feature of the eye.
 27. The method according to claim25, wherein the step of measuring the amount of contact comprisesoperating a strain gauge.
 28. The method according to claim 25, furthercomprising stopping, using the controller, the moving of the eye contactportion in response to the controller determining that the specifiedamount of contact between the eye contact portion and the feature of thehas been established.
 29. The method according to claim 19, wherein theeye contact portion is moved relative to the positioning system by anelectromechanical device.
 30. The method according to claim 29, furthercomprising providing a signal from the controller to theelectromechanical device, the electromechanical device moving the eyecontact portion relative to the positioning system in response to thesignal being received by the electromechanical device.
 31. The methodaccording to claim 29, wherein the electromechanical device isconfigured to transduce rotational movement provided by a motor intolinear movement of the eye contact portion.